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Shifts in the diet of Lake Ontario alewife in response to ecosystem change

Journal of Great Lakes Research

By:
, , and
DOI: 10.1016/j.jglr.2008.12.010

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Abstract

In the 1990s, the Lake Ontario ecosystem was dramatically altered due to continued invasions of exotic species including dreissenid mussels and predatory cladocerans. We describe the diet and biomass of prey in the stomachs of adult (≥ 109 mm TL) and sub-adult (< 109 mm TL) alewife (Alosa pseudoharengus) in 2004 and 2005 across seasons and depths and compare our results to data from 1972 to 1988. During 2004 and 2005, adult alewife consumed primarily zooplankton prey at bottom depth zones < 70 m and primarily Mysis at bottom depth zones > 70 m. Mysis dominated the diets of adult alewife in all seasons except during the summer of 2004 when zooplankton dominated. Mysis dominated the diets of sub-adult alewife during early and late spring and zooplankton dominated the diets in summer and fall. Bythotrephes and Cercopagis were observed in the diets of both sub-adult and adult alewife. Diporeia was observed only rarely in adult alewife diets. The biomass of prey in alewife stomachs varied seasonally and increased with bottom depth for adult alewife. Alewife diets in 2004–2005 differed from those in 1972 and 1988 with an increase in the prevalence of Mysis, and a decline in the prevalence of zooplankton. The biomass of prey in adult alewife stomachs declined in 2004 and 2005 compared to 1972 and 1988, at bottom depth zones < 70 m but not at bottom depth zones > 70 m suggesting reduced food availability closer to shore. We hypothesize that consumption levels at the shallower depth zones, as indicated by very low biomass of prey in alewife stomachs, may not be sufficient to sustain alewife growth. The increased prevalence of Mysis and common occurrence of predatory cladocerans in the diet of alewife means that alewife have shifted to a higher trophic position.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Shifts in the diet of Lake Ontario alewife in response to ecosystem change
Series title:
Journal of Great Lakes Research
DOI:
10.1016/j.jglr.2008.12.010
Volume
35
Issue:
2
Year Published:
2009
Language:
English
Publisher:
Elsevier
Publisher location:
Amsterdam, Netherlands
Contributing office(s):
Great Lakes Science Center
Description:
9 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Great Lakes Research
First page:
241
Last page:
249
Other Geospatial:
Lake Ontario